Lo Zingarelli is the classic modern Italian dictionary - it is a single language, not an Italian/English dictionary.

Described as a Vocabolario della Lingua Italiana di Nicola Zingarelli, it is published by the Zanichelli publishing house in two volumes, and is rather expensive.

The more modest, single volume Zingarelli minore is better value for the student of Italian. It is heavily illustrated, and contains many useful appendices.

See also Nicolo Antonio Zingarelli, the Italian composer.